Holocene underkill.

I n this issue of PNAS, Jones et al. (1) address an issue that has been with us, in one way or another, for some 200 years. Around the year 1800, French paleontologist Georges Cuvier established the reality of vertebrate extinction by using animals so large that their future discovery on the hoof was highly unlikely (2). Included on the list were some now known to have been late Pleistocene in age, including mammoth and mastodon. As time went on, the list of extinct American and Eurasian mammals of this age grew hand in hand with our understanding of the geological deposits in which the fossils were embedded. As this happened, it became harder and harder to understand why all of these extinctions had occurred. Things became even more complex in 1859, not because of the publication of Darwin’s On the Origin of Species, but because that year also saw the recognition that the animals had actually coexisted with humans (3). Such coexistence raised the possibility that the extinctions had happened at least in part because of human hunting. Soon after 1860 many scientists agreed that people must have played some role in causing the losses.